Detrusor myoplasty and neuro-muscular electrical stimulation

ABSTRACT

An implantable micturition inducer is disclosed. The device comprises an implantable actuatable signal generator that comprises one or more switches and a power source, and at least one electrical lead having one end connected to the signal generator and the other end adapted to be connected to muscle transected to form a muscle bag around an individual&#39;s bladder. Actuation of the switch or switches results in the delivery of a series of stimulus pulses from the signal generator to the muscle bag which are sufficient to cause the muscle bag to contract and thereby induce micturation on demand. Methods for inducing micturition in patients with areflexic bladders or an otherwise diminished capacity to intentionally micturate are disclosed.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the National Stage application of PCT ApplicationNumber PCT/US94/13959 filed Dec. 6, 1994, which is acontinuation-in-part application of Ser. No. 08/166,211, filed Dec. 13,1993, which issued Dec. 6, 1994 as U.S. Pat. No. 5,370,670.

FIELD OF THE INVENTION

The present invention relates to a method of inducing micturition inindividuals who are otherwise with a diminished ability or without theability to do so. This application is U.S. Pat. No. 5,370,670, which isincorporated herein by reference.

BACKGROUND OF THE INVENTION

Functional neuromuscular electrical stimulation (FNS) to restore controlover deficient muscular functions has been used as a clinical treatmentof motor deficiencies for the last 20 years (Hambrecht, F. T., Reswick,J. B., (eds): Functional Electrical Stimulation: Application in NeuralProstheses. New York N.Y., Marcel Dekker, 1977). Applications includerespiratory assistance by stimulation of the diaphragm in quadriplegicpatients, and neuroprosthesis of the arms and legs (Hambrecht, F. T.,Reswick, J. B., (eds): Functional Electrical Stimulation: Application inNeural Prostheses. New York N.Y., Marcel Dekker, 1977; Mortimer, J. T.:Motor prostheses, in Brooks (ed): Handbook of Physiology, the NervousSystem. Motor Control, Bethsda, Md., 1984 Am Physiol. Soc. 2:155-187;Salmons, S. and Vrbova, G. 1969 J. Physiol. 201:535). Some of thesestudies have indicated that changes in muscle function occur based onthe stimulation. It is known that muscle fiber composition and resultingphysiologic and metabolic characteristics (force, contraction andrelaxation times) depend on neural activity (Salmons, S. and Vrbova, G.1969 J. Physiol. 201:535). By electrically controlling nerve and muscleactivation, improved fatigue-resistance of atrophic, paralyzed musclesin quadriplegic patients has been reported (Peckham, H. et al. 1976Clin. Orthop. 114:326.)

In most FNS applications, electrical stimulation is applied to musclesin situ to restore or supplement function. Recently, researchers haveevaluated the use of FNS to control the function of heterotopicallytransferred skeletal muscles. In some cases, the muscle may perform orwork very differently from its original function. Dynamiccardiomyoplasty is a procedure in which a skeletal muscle graft isapplied to the myocardium and trained to contract in synchrony with theheart muscle (Chachques, J. C., et al. 1988 Circulation 78:203 (Suppl3); Acker, M. A., et al. 1987 Science 236:324; Magovern, G. J., et al.1988 Ann Thorac. Surg. 45:614). The first clinical cardiomyoplasty wasperformed in 1985 (Carpentier, A. and Chacques, J. C.: 1985 Lancet1:1267). In the approach followed by those investigators, the latissimusdorsi muscle was conditioned to behave like a cardiac muscle by slowlyincreasing muscle work to adapt to a new cardiac-like function. It isestimated that over 100 cardiomyoplasties have been performed world-wideand may represent an important role in the treatment of congestive heartfailure.

In the 1960's the concept of the application of functional electricalstimulation in urology began to emerge. Direct bladder surfacestimulation was attempted in order to induce micturition by a patient.However, many clinicians became disenchanted because the high currentrequired would spread to the pelvic floor mixture, causing pain andcontraction of the external sphincter during micturition. Device failurewas common and a fibrocapsule often developed around the bladderelectrodes (Alexander, S. and Rowan, D., 1968 Br. J. Surg., 55:358;Boyce, W. H., et al. 1964 J. Urol., 91:41; Merrill, D. C. 1974 J. Urol.112:823; Merrill, D. C. and Conway, C. J. 1974 J. Urol. 112:52; and,Timm, G. W. and Bradley, W. E. 1969 Invest. Urol. 6:562).

Throughout the 1970 and 1980's, research toward bladder stimulation wasdirected toward sacral anterior root stimulation in conjunction withselective or complete sacral deafferentation (Brindley, G. S. et al.1986 J. Neurol. Neurosurg. & Psychiatry 49:1104; and, Tanagho, E. A. etal. 1989 J. Urol. 142:340). Sacral anterior root stimulation requiresintact sacral motor roots and a detrusor capable of contraction.

The use of the rectus muscle to assist manual-compression bladderemptying has been reported (Zhang, Yu-Hai et al., 1990 J. Urol.144:1194). A rectus muscle sling to suspend the bladder to a levelimmediately beneath the anterior rectus sheath was used, therebyallowing neurologically injured patients to empty their bladder withmanual compression. The skeletal muscle flap has also been described forbladder augmentation. Direct anastomosis between skeletal muscle and thebladder wall will develop ingrowth and resurfacing of the muscle withtransitional cells. Calculi and cartilaginous formation commonly occurhowever, complicating this technique (Buyukunal, S. N. C., et al. 1989J. Ped. Surg. 24:586).

There is a need for an improved method of inducing micturition by anindividual with an areflexic bladder. There is a need for methods ofelectrical muscle stimulation to induce micturition by an individualwith an areflexic bladder.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a system and method forinducing micturition in patients with areflexic bladders or an otherwisediminished capacity to intentionally micturate.

The present invention provides an implantable micturition inducer. Thedevice that is the invention comprises an implantable actuatable signalgenerator that comprises one or more switches and a power source, and atleast one electrical lead having one end connected to the signalgenerator and the other end adapted to be connected to muscle transectedto form a muscle bag around an individual's bladder. Actuation of theswitch or switches results in the delivery of a series of stimuluspulses from the signal generator to the muscle bag which are sufficientto cause the muscle bag to contract and thereby induce micturation ondemand.

The present invention provides a method wherein the a muscle for apatient is transected and used to form a muscle bags around thepatient's bladder or a reconstructed, augmented or created bladder. Themuscle bag is attached to at least one electrical lead which is attachedto an implantable actuatable signal generator that comprises one or moreswitches and a power source. The switch or switches of the signalgenerator are actuated and a series of stimulus pulses are deliveredfrom the signal generator to the muscle bag which are sufficient tocause the muscle bag to contract.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1A is a diagram showing the human rectus abdominis muscle includinginnervation and vascularization, the points of attachment of the rectusabdominis muscle, and the bladder before detrusor myoplasty.

FIG. 1B is a diagram showing the human rectus abdominis muscle includinginnervation and vascularization, the points of attachment of the rectusabdominis muscle, and the bladder wrapped with the rectus muscle flapafter detrusor myoplasty.

FIG. 2A contains data showing twenty-four hour micturition patterns of acontrol rat.

FIG. 2B contains data showing twenty-four hour micturition patterns of aspinal cord injured rat.

FIG. 2C contains data showing twenty-four hour micturition patterns of aspinal cord injured rat after detrusor-myoplasty.

FIG. 3 shows an electromyographic recording of rectus muscle electricalpotentials with nerve stimulation in a rat 4 weeks after spinal cordinjury and detrusor-myoplasty. Single stimulation parameters: A) 50 V,0.5 msec, and B) 100 V, 0.5 msec. Note the M wave potentials indicatingviable innervation of the muscle flap.

FIG. 4A contains data showing the effect of stimulus voltage on bladderpressure. Stimulation parameters: 0.5 msec duration at 20 Hz for 2seconds at voltage between 10-200 V. Nerve-stimulation of control rats,nerve-stimulation of spinal cord injured (SCI) rats, muscle-stimulationof control rats, and muscle-stimulation of SCI rats.

FIG. 4B contains data showing the effect of stimulus duration on bladderpressure. Stimulation parameters: 0.5 msec duration at 200 V and 20 Hzwith stimulus durations between 1-15 sec. Four groups of rats werestudied: Nerve-stimulation of control rats, nerve-stimulation of spinalcord injured (SCI) rats, muscle-stimulation of control rats, andmuscle-stimulation of SCI rats.

FIG. 5A contains data showing the effect of pulse duration on maximalbladder pressure after nerve and muscle stimulation in spinal cordinjured rats. Stimulation parameters: 200 volts, 20 Hz for 2 seconds atpulse duration from 0.05 to 0.5 msec.

FIG. 5B contains data showing the effect of stimulus frequency onmaximal bladder pressure after nerve and muscle stimulation in spinalcord injured rats. Stimulation parameters: 0.5 msec, 200 V for 2 secondsat frequency from 1 to 50 Hz.

FIG. 6A contains data showing bladder pressure response todetrusor-myoplasty neurostimulation in a spinal cord injured rat. Nervestimulation: 50 V, 0.05 msec, and 50 for 2 seconds.

FIG. 6B contains data showing bladder pressure response todetrusor-myoplasty neurostimulation in a spinal cord injured rat. Nervestimulation: 25 V, 0.05 msec, and 50 Hz for 4 seconds.

FIG. 6C contains data showing bladder pressure response todetrusor-myoplasty neurostimulation in a spinal cord injured rat. Musclestimulation: 50 V, 0.05 msec, 50 Hz for 14.6 seconds.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to devices and methods of inducingmicturition in individuals with areflexic bladders. According to thepresent invention, a neurovascular muscle flap is surgically wrappedaround the bladder. The muscle is attached to an implantable actuatablebattery powered signal generator such that activating the signalgenerator neurostimulates the muscle which thereby contracts and inducesmicturition.

According to the preferred embodiments of the present invention, therectus abdominis muscle serves as a neurovascular muscle flap fordetrusor-myoplasty wherein the muscle is used to wrap around thebladder. In other embodiments, the internal oblique is used to createthe muscle flap. In other contemplated embodiments, the latimus dorsi isused as a muscle tissue source which is transected, revascularized,renervated and attached with electric leads to the implantableactuatable signal generator.

In some embodiments, the bladder is reconstructed or augmented by orcreated from other tissue such as intestinal tissue. Bladders may bereconstructed in cases where the individual is suffering from bladdercancer and malignant tissue has been resected. In such cases, thereconstructed bladder may be augmented or enlarged by addition ofintestinal tissue. In some embodiments, the individual's bladder iscompletely removed and a new bladder is created from intestinal tissue,particularly small intestine or colon. The reconstructed or newlycreated bladder is wrapped with a muscle flap and connected to animplanted actuatable signal generator by electric leads which arespecifically adapted to connect the muscle to the implantable actuatablesignal generator.

There are a large number of patients with areflexic bladders who may becandidates for detrusor-myoplasty. These patients are excluded fromanterior root neurostimulation because they do not have an intact sacralmotor root and/or their bladders cannot contract. Detrusor-myoplasty maybe applicable for patients with non-intact sacral motor roots who arenot candidates for sacral nerve root stimulation. Detrusor-myoplastywith neurostimulation can provide an alternative therapy for upper motorneuron neurogenic bladder dysfunction.

Detrusor-myoplasty is based on the principles of cardiomyoplasty. Muscleis transected in order to provide a contractile source to effect organfunctioning. In the case of detrusor-myoplasty, muscle is wrapped aroundthe bladder to substitute for non-functioning muscle. A source ofelectrostimulation is provided to initiate contraction and inducemicturition. There are several potential advantages todetrusor-myoplasty over cardiomyoplasty: 1) muscle fatigue is less of aproblem because muscle contraction for bladder emptying only need tooccur 10 times or less per 24 hours versus 60 contractions per min forthe heart; and 2) acute mechanical or electronic failure can be treatedwith intermittent catheterization, failure of cardiomyoplasty couldimmediately jeopardize the life of the patient.

The rectus abdominis muscle was found to be best suited as aneurovascular muscle flap for detrusor-myoplasty. The rectus muscle wasexamined in detail in the rat, goat, and human cadaver. FIG. 1A is adiagram showing the human rectus abdominis muscle including innervationand vascularization, the points of attachment of the rectus abdominismuscle, and the bladder before detrusor myoplasty.

FIG. 1A represents a preferred embodiment of the invention. As shown inFIG. 1A, the rectus abdominis muscle 1 arises from the pubic symphysisand the pubic crest, collectively shown as 7 and inserts on the fifth,sixth, and seventh costal cartilages above the costal margin,collectively shown as 8. The muscle 1 is a long and flat muscle that istransected by three tendinous intersections. It is partially ensheathedby the anterior and posterior rectus sheaths, and extends the length ofthe anterior abdominal wall. The rectus abdominis 1 has two majorarterial pedicles. The upper pedicle is a continuation of the internalthoracic artery 3 and the lower pedicle is a branch of the externaliliac artery 6. These two arterial supplies anastomose in the mid-bellyof the rectus muscle 1. There are numerous musculocutaneous perforatingvessels throughout the muscle. The axial vascularization is predominanthowever, with the deep inferior epigastric artery 5 more significantthan the superior epigastric artery 4. The inferior epigastric artery 5is anatomically larger and physiologically "dominant" over the superiorepigastric artery 4 with respect to blood supply to the muscle 1. Themuscle 1 receives segmental innervation from the branches of the lowersix intercostal nerves 9-14. Motor branches from the seventh throughtwelfth intercostal nerves 9-14 reach the muscle 1 at its deep surface.These nerves 9-14, together with the intercostal arteries, pass betweenthe versus abdominis and the internal oblique muscles. They give severalbranches to the external and internal oblique muscles, then end in twoperforating branches. One is a lateral cutaneous branch, the other amedial somatomotor branch that penetrates the rectus muscle 1. Long-termfollow-up of patients after rectus abdominis muscle transfer for breastreconstruction has demonstrated no significant functional deficits. Thesacrifice of this muscle does not negatively impact the patients'ability to move.

Detrusor myoplasty is performed as follows. As shown in FIG. 1B, themuscle 1 is transected free from the rectus fascia. The blood supplyfrom the superior epigastric artery 4 is sacrificed and the muscle istransected midway between the xiphoid and umbilicus. The inferiorepigastric artery 5 is carefully preserved. The muscle flap attached tothe symphysis pubis 7 is located and used to wrap/cover the bladder 2without tension, preserving at least two 13-14, preferably two 13-14 tofour 11-14, intercostal nerves with its blood supply. Approximately 1/2to 2/3 of the entire unilateral rectus muscle 1 is needed to effectivelywrap the bladder 2. The muscle 1 is wrapped around the distended bladder2 and attached to itself with sutures 18, creating a muscle "jacket" or"bag" with its content being the bladder 2. An actuatable signalgenerator, also referred to herein as an electrostimulator or anelectrostimulation system, which includes a signal generator 15, one ormore sets of leads 16 and a switch 17 is provided. Electrostimulatorsare similar to those commercially available and used in cardiomyoplastyand may be assembled from readily available components. Signalgenerators and leads such as those sold by Medtronic (Minnesota) may bemodified for use in detrusor myoplasty. Generally, theelectrostimulators used in detrusor-myoplasty are more simple in designand function than those used in cardiomyoplasty which must functioncontinually synchronous with the heart. The electrostimulator isimplanted in the patient and at least one set of leads 16 is connectedfrom the signal generator 15 to one or more of the motor nerves attachedto the muscle bag (two to four intercostal nerves being attached to themuscle bag: 13, 14; 12, 13, 14; or 11, 12, 13, 14) and/or muscle flap 1for delivery of a pulse thereto.

Signal generators 15 useful in the present invention include signalgenerators that can deliver a series of pulses at a frequency in therange of 1 to 50 Hz, 0.01 to 1.0 msec pulse duration, 1 to 300 voltsamplitude and a stimulation duration of up to 3 minutes. It is preferredthat signal generator 15 is battery powered and implantable. The signalgenerator 15 may be of any standard design to provide such pulses; theshape of the pulses is not critical to the invention as claimed.

Examples of switches 17 useful in the method include standard electricalswitches, radiofrequency controlled electromagnetic switches and magnetactuated switches. It is preferred that the switch is an implantableradiofrequency controlled electromagnetic switch. In some embodiments,two switches are provided to reduce the probability of accidentalactuation of the signal generator 15. In some embodiments, the switch isan implantable radiofrequency controlled electromagnetic switch in whichtwo frequencies are used to actuate the switch in order to reduce theprobability of accidental actuation of the signal generator 15. Althoughthe switch 17 is illustrated as a separate component, it can be designedto be integral with the signal generator unit so long as it performs thefunction of controlling delivery of pulses from the signal generator 15.

Examples of leads 16 useful in the method include spiral nerveelectrodes or wire extramuscular leads.

The signal generator 15 and switch 17 may be external or internal,preferably internal. Preferably, the internalized device is placed inthe subcutaneous tissue in the lower abdominal area.

Electrical stimulation is preferably applied to two motor nerves ordirectly to the muscle flap 1. Skeletal muscle contractions arecontrolled in magnitude and duration by the parameters of electricalstimulation. A single pulse results in a short evoked twitch contractionand a brief rise in intravesical pressure. Pulse width and amplitudemodulation enables gradation of response by varying the number ofactivated motor units (spatial and temporal recruitment). Maximalbladder pressure increased as the frequency, pulse duration, voltage, orstimulation period were increased. Stimulation parameters range from afrequency of 1 to 50 Hz, 0.01 to 1.0 msec pulse duration, 1 to 300 voltsamplitude and a stimulation duration of up to 3 minutes. Frequenciesfrom 10 to 35 Hz, preferably 10-30 Hz, and voltages from 1 to 50 voltsinduce maximum bladder contraction and voiding. A pulse duration of 0.05to 0.5 is preferred. A pulse duration of 0.3 to 0.5 msec is optimal. Astimulation duration of 0.2 to 1 minute is preferred. The ability ofmuscle to produce long-lasting work, as demonstrated by sustainedincreases in intravesical pressure, depends on stimulus amplitude,duration, and frequency.

EXAMPLES Example 1

Detrusor-myoplasty (skeletal muscle assisted micturition) wasinvestigated in a rat model of spinal cord injury (SCI).Detrusor-myoplasty was done in control and SCI rats and studied afterone month. The rectus muscle on one side of the abdomen was dissectedfree from the ventral fascia and transected cephalad, above the level ofthe umbilicus. The muscular insertion to the symphysis pubis was leftintact. Vascular flow via the inferior epigastric artery and vein waspreserved. Innervation by 2 to 3 intercostal motor nerves was leftintact. Postoperatively, no bowel or abdominal wall functional deficitwas apparent. The rotated muscular flap remained innervated andvascularized. No difference in 24 hr micturition patterns became evidentbetween control rats and rats with a rectus muscle-wrapped bladder whennot stimulated. Stimulation of the rectus muscle-wrapped bladder (bothnerve and direct muscle stimulation) was capable of generating bladderpressure (range 10 to 55 mmHg) and achieved bladder emptying.Stimulation parameters ranged from 0.05-0.5 msec duration, 1-50 Hz, and12.5-300 volts. Less voltage was required for nerve than musclestimulation to achieve similar intravesical pressure. In both acuteexperiments and in rats surviving 1 month after spinal cord injury,sustained bladder contractions continued.

Materials and Methods

Rats:

Male Sprague-Dawley rats (Charles River Laboratories, Wilmington,Mass.), weighing 250-300 gm were used. Four groups of rats werestudied: 1) sham spinal cord injury (SCI) (n=8); 2) sham SCI withdetrusor-myoplasty (n=5); 3) SCI rats (n=8); and 4) SCI rats withdetrusor-myoplasty (n=5). The research protocol and animal usage inthese studies have been approved by our Institutional Animal Care andUse Committee, and adhere to guidelines set forth by the US Departmentof Health, Education and Welfare's "Guide for the Care and Use ofLaboratory Animals".

Anesthesia:

Anesthesia was induced in all animals using pentobarbital (65 mg/kg,intraperitoneally), with pure oxygen delivered intraoperatively througha tight-fitting mask. In all animals, rectal temperature was maintainedbetween 37° C. and 38° C. with a heating pad.

Spinal Cord Injury:

After a sufficient depth of anesthesia was verified, the animal waspositioned in a spinal stereotaxic apparatus (David Kopf, Tujunga,Calif.), with fixation at the ears. The skull was exposed, andstainless-steel jewelers' screws (Small Parts, Miami, Fla.) implantedfor recording the somatosensory-evoked potential (SEP). Screws werethreaded as electrodes into the skull near the union of the midline withbregma (positive) and lambda (negative) and in the nasal sinus. Stimuliwere delivered through a pair of platinum subdermal needle electrodes(Grass, Quincy, Mass.) inserted in the hindlimb near the medialmalleolus and plantaris tendon. Constant voltage pulses were deliveredat 3 Hz at an intensity sufficient to elicit a slight twitch in theouter digits (10 to 15 V). SEPs were averaged over a 90-millisecondepoch using 256 trials and a bandpass between 3.2 and 3,2000 Hz. Thelatency and amplitude of the major negative wave were then measured overthree to five trials prior to laminectomy.

The thoracic region of the spine was then exposed, and laminectomyperformed at the T-10 level. The dura mater was left intact. The SEP wasthen re-evaluated in order to confirm the presence of normal conductionafter laminectomy. Animals were excluded from study if the SEP latencyincreased by more than 2 milliseconds or if the amplitude decreased bymore than 50%. Animals were prepared for injury by applying additionalfixation at the T-12 spinous process using a vertebral clamp.

The injury device consisted of a hollow steel tube with a nylonimpounder at the bottom (0.3 cm diameter at the tip). The impounder wasfree to move up into the tube but was restricted in its downwardmovement. After being secured to a micromanipulator, the device, withimpounder tip fully extended, was lowered onto the exposed dura untilcontact with the cord caused the impounder to move precisely 0.2 cm upinto the tube. At this point a 10 gm weight was dropped from a height of5 cm to provide a 50 gm cm injury. Sham-injured rats underwent theimpounder placement but without weight-drop. The SEP was then recorded2, 5, 10, and 15 minutes later in order to verify the injured condition.Animals (groups 3 and 4) subjected to spinal cord injury were excludedif the SEP response was not obliterated during the entire 15 minuteperiod following weight-drop. Similarly sham-injured animals (groups 1and 2) were excluded if the SEP latency increased by 2 msec or amplitudedecreased by ≧50%.

Neurological Evaluation:

A modified Tarlov scale (Tarlov, I. 1954 Arch. Neurol. Psychiatry71:588) was employed weekly for 4 weeks. Each hindlimb was rated asfollows:

0--total paraplegia of hindlimbs;

113 no spontaneous movement but responds to hindlimb pinch;

2--spontaneous movement but unable to stand;

3--able to support weight but cannot walk on broad, flat surface;

4--able to walk on broad, flat surface;

5--able to walk on broad, flat surface and support weight on a1.8-cm-wide ledge; and

6--able to walk on ledge.

The final scores are reported. The Rivlin-Tator angleboard test (Rivlin,A. S. and Tator, C. H. 1977 J. Neurosurg. 47:577) was also performedweekly and before the animals were sacrificed. The maximum anglemaintained for 5 seconds or longer was measured, and averaged to yield afinal value.

Micturition Patterns:

The rats were placed in a metabolic cage that could deflect the voidedurine. The deflected urine was collected for 24 hour periods on anelectronic scale (Scientech ESL/1000; Boulder, Colo.) and constantlymonitored by a microcomputer for the recording of micturition frequency,duration, and volume. Data were recorded and stored using Lotus Measuredata acquisition software (National Instruments, Austin, Tex.).

Parameters analyzed were: 1) total urine volume/24 h; 2) number ofmicturitions/24 h; 3) mean volume of each void; 4) oral fluid intake/24h; 5) ratio of micturitions-night vs. day; 6) largest micturitionalvolume; and 7) smallest micturitional volume.

Detrusor-Myoplasty Technique:

Unilateral dissection under magnification was directed to the rectusabdominis muscle using a midline incision. The entire width of themuscle was elevated creating a muscle flap averaging six centimeters inlength. The muscle was transected cephalad, above the level of theumbilicus. The attachment to the pubic symphysis and the inferiorepigastric artery were carefully preserved. Laterally, 2 to 3intercostal motor nerves were elevated to the rib tips and preservedwith the muscle flap. The bladder was then exteriorized, cannulated atthe level of the urethra using a modified 18 Gauge spinal needle, andconnected to a Statham P-23 pressure transducer. At this point themuscle was wrapped around the distended bladder and sutured (3-0Vicryl^(R)) to itself, creating a muscle bag, with its content being thebladder. In another 3 SCI rats that underwent detrusor-myoplasty, a 20gauge intravenous infusion catheter was sutured to the dome of thebladder. Micturition could thereby be directly observed at the urethralmeatus after electrostimulation.

Electrical Stimulation:

Stimulation parameters ranged from a frequency of 1 to 50 Hz, 0.05 to0.5 msec pulse duration, and 12.5 to 300 volts amplitude. Electricalstimulation was applied to two motor nerves or directly to the muscleflap.

Blood Flow Measurement:

Blood flow within the muscle was monitored by laser Doppler flowmetry(BMP 403A, LaserFlow Inc., St. Paul, Minn.). The probe was placed on thesurface of the muscle belly to continuously monitor blood flow in 1 mm³of the underlying cape beds during stimulation.

Data Analyst:

Parametric measures were compared via analysis of variance (ANOVA)followed by Tukey's post-hoc analysis. Ordinal neurologic outcome scoreswere compared by the Kruskal-Wallis ANOVA followed by the Mann WhitneyU-test. A p value less than 0.05 for both the ANOVA and post-hoc testwas considered significant.

Results

The median final neurological outcome as measured by the modified Tarlovratings for all animals who survived 30 days after spinal cord injurywas 5, reflecting the presence of spontaneous movement both hindlimbs,weight-bearing ability in one hindlimb, but the absence of locomotorfunction. Sham operated SCI rats that did and did not undergodetrusor-myoplasty all had normal final Tarlov scores of 12. Creation ofdetrusor-myoplasty did not alter Tarlov ambulation scores or theinclined angle scores (Table 1).

Analysis of 24 hr micturition patterns demonstrated no differences inoral fluid intake/24 hr, voided volume/24 hr, and ratio of number ofmicturitions during the night vs day among the four groups. Spinal cordinjured rats with and without detrusor-myoplasty had a significantdecrease in the number of micturitions/24 hr, an increase in volume permicturition, and greater largest and smallest micturition volumes (Table2, FIG. 2A, FIG. 2B and FIG. 2C). The micturition patterns were similaramong rats in both the sham and SCI groups with and withoutdetrusor-myoplasty. The performance of detrusor-myoplasty withoutelectrical stimulation did not enhance or interfere with the functionalstatus of the rat based on Tarlov locomotor score, angleboard score, andmicturition patterns.

No complications from the procedure of muscle-wrapping developed;neither hernia nor bowel obstruction were seen. Two rats died within 5days after the initial spinal cord injury, and both manifested urinarytract sepsis.

Laser Doppler flowmetry displayed similar blood flow values in therectus muscle flap immediately after superior epigastric division, and 1month after muscle transposition. Muscle blood flow values for the flapand the contralateral undissected rectus muscles were not significantlydifferent at 97±34 and 105±40 (ml/100 g tissue min.), respectively(p=0.47). Similar blood flow values were seen before, during, and afterelectrical stimulation.

Skeletal muscle contractions could be controlled in magnitude andduration by the parameters of electrical stimulation. A single pulseresulted in a short evoked twitch contraction and a brief rise inintravesical pressure (FIG. 3). Pulse width and amplitude modulationenabled gradation of response by varying the number of activated motorunits (spatial and temporal recruitment). Maximal bladder pressureincreased as the frequency, pulse duration, voltage, or stimulationperiod were increased. Frequencies from 10 to 35 Hz and voltages from150 to 300 volts induced maximum bladder contraction and voiding. A longpulse duration 0.3 to 0.5 msec was optimal. The ability of muscle toproduce long-lasting work, as demonstrated by sustained increases inintravesical pressure, depended on stimulus amplitude, duration, andfrequency (FIG. 4A, FIG. 4B, FIG. 5A and FIG. 5B).

Both nerve and direct muscle stimulation were able to generate detrusorcontraction and increase intravesical pressure. The rectus musclecontraction and increase in intravesical pressure was sustained for theduration of electrical stimulation (FIG. 6A, FIG. 6B and FIG. 6C). Themaximal detrusor pressure was similar between sham and SCI rats that haddetrusor-myoplasty. Bladder emptying could be achieved with both nerveand muscle stimulation. Less stimulation voltage was required for nerveversus direct muscle stimulation to achieve bladder emptying.

Example 2

Detrusor-myoplasty dissection was also performed in 2 female goats. Therectus abdominis muscles were used for bladder wrapping. The goatbladder is a pelvic organ of greater than 100 ml in capacity withdetrusor wall thickness similar to the human. The rectus muscle in thegoat is wide but thin. The rectus muscle was dissected free from theoverlying fascia while preserving 2 motor nerves. The muscle flap,attached only interiorly to the pubic symphysis, could reach and wraparound the bladder without tension. Considering the similarity in sizeand proportion of goat anatomy, the goat is a good chronicdetrusor-myoplasty model for human study.

Example 3

Rectus abdominis muscles were used for bladder wrapping in 3 fresh humancadavers (2 female, 1 male). In all 3 human cadavers it was possible todissect the rectus muscle in its entirety and isolate and preserve 3motor nerves. Dissection of cadavers confirmed the segmental innervationof the rectus abdominis muscle by the terminal branches of the lower sixintercostal nerves. The nerves pass with the intercostal arteries deepto the internal oblique muscle and superficial to the versus abdominismuscles. The nerves penetrate the sheath of the rectus muscle lacy toenter the muscle belly ventrally. The muscle was dissected free from therectus fascia, leaving only the attachment to the symphysis pubis. Theblood supply from the superior epigastric artery was sacrificed and themuscle was transected midway between the xiphoid and umbilicus. Theinferior epigastric artery was carefully preserved. The muscle flap waslocated and used to wrap the bladder without tension, preserving 3nerves with its blood supply. Approximately 1/2 to 2/3 of the entireunilateral rectus muscle is needed to effectively wrap the bladder. Nodifficulty in abdominal closure occurred.

Example 4

Transection of the rectus abdominis muscle around the bladder wasperformed on a patient. Neurovascular innervated rectus abdominis musclewrap of the urinary bladder restored micturition. The patient was a33-year old male paraplegic who suffered an L₄₋₅ spinal cord injurysecondary to a gunshot wound to the spine in 1980 and who has beenmanaged with a suprapubic tube since the injury. The patient complainedof constant suprapubic pain, leakage of urine per urethral meatus andrecurrent febrile urinary tract infections. Video-urodynamicsdemonstrated a poorly compliant bladder with a capacity of less than 100ml and grade II left vesicoureteral reflux.

Surgery was done through a midline abdominal incision and the suprapubictract was excised. Bladder augmentation was first done using 15 cm ofthe terminal ileum. The isolated ileum was detubularized and anastomosedto the bladder which was opened in a clam fashion. The entire width ofthe left rectus muscle was elevated and transected cephalically abovethe level of the umbilicus. The inferior pubic symphysis attachment andinferior epigastric artery were preserved. Laterally, 3 intercostalmotor nerves were elevated to the rib tips and preserved with the muscleflap. At this point the muscle was wrapped around the augmented bladderand sutured (0 Vicryl^(R)) to itself, creating a muscle bag, with itscontent being the bladder.

The postoperative course was remarkable for a bout of pseudomembranouscolitis. The patient has sensation of filling and fullness. No urineleakage or bladder perforation occurred. Intermittent cleancatheterization was instituted on the seventh postoperative day. Nobowel or abdominal wall functional deficit was apparent. After 30 daysthe patient was taught to volitionally contract his rectus muscle tourinate.

Example 5

The following is a description of the detrusor-myoplasty in which anelectrostimulation system is attached to a transected rectus abdominismuscle wrapped around the urinary bladder to restore micturition.Briefly, surgery is done through a midline abdominal incision and thesuprapubic tract is excised. Bladder augmentation is first done using 15cm of the terminal ileum. The isolated ileum is detubularized andanastomosed to the bladder which is opened in a clam fashion. The rectusabdominis muscle is used for detrusor-myoplasty. The entire width of theleft rectus muscle is elevated and transected cephalically above thelevel of the umbilicus. The inferior pubic symphysis attachment andinferior epigastric artery are preserved. Laterally, 3 intercostal motornerves are elevated to the rib tips and preserved with the muscle flap.At this point the muscle is wrapped around the augmented ladder andsutured (0 Vicryl^(R)) to itself, creating a muscle bag, with itscontent being the bladder. An electrostimulator which includes a powersupply, leads and a switching mechanism is provided internally. Theleads are attached to the rectus abdominis muscle and/or one or more ofthe intercostal motor nerves. The other end of the lead is attached tothe power supply by way of the switch. The following is a detaileddescription of the procedure.

The patient is placed supine on the operating table. The patient'sabdomen and genitalia are prepped and draped in the usual sterilefashion. The patient is anesthetized and intubated. A lower abdominalmidline incision is made around, and the suprapubic tract is isolated byincising on both sides. Dissection is carried down to the anteriorrectus fascia which is incised with Metzenbaum scissors. The anteriorrectus sheath is then opened using electrocautery. The dissection isthen carried down to the peritoneum which is grasped with forceps andincised. The peritoneum is then entered. The suprapubic tract isisolated and the skin surrounding the tract is grasped using Allis clampand the entire tract is excised using sharp and blunt dissection all ofthe way down to the bladder which is then opened at the suprapubic tractsite.

The bladder is freed from adhesions. A midline incision is made in thebladder from the posterior wall all of the way down to the bladder neckanteriorly. Hemostasis is achieved using electrocautery. A segment ofsmall bowel approximately 1 foot proximal to the ileocecal valve isisolated. Incisions are made in the mesentery, taking care to preservethe blood supply to the segment of bowel, approximately 10 inches inlength. Using clamps and 3-0 silk ties, the mesentery is incised andligated, and the ileum is resected using GIA stapler. The ileum is thenreconstituted using a stapled anastomosis. This is reinforced using 3-0silk interrupted sutures. The anastomosis is created using TIA stapler,taking care to use it on the anti-mesenteric border.

The segment of ileum is then swung down to the bladder and itsanti-mesenteric border is incised. The segment of bowel is then used toaugment the bladder in such a way as the piece of ileum is then suturedto the bladder wall using 0 Vicryl sutures in running fashion. Suturingthe ileum and bladder creates a water-tight seal which is confirmed byputting saline in through the Foley catheter. Any small leaks aresutured shut using interrupted 0 Vicryl.

Next, attention is turned to the left rectus abdominis muscle. Therectus fascia is incised medially and the rectus is dissected free ofthe posterior and anterior rectus sheaths, using sharp and bluntdissection. The superior epigastric vessels are identified and ligated.The rectus abdominis muscle is then transected several cms below thecostal margin. The lateral neurovascular bundles are then identifiedsegmentally from about the level of the T10 or T11. These nerves aretraced back along the lateral abdominal wall, so as to free them up fromtheir surrounding tissues. Gradually, the rectus abdominis muscle isbrought down further and further into the pelvis. The muscle with itsnerve supply intact is then wrapped around the neobladder, and suturedto itself and bladder using 0 Vicryl interrupted sutures. A nervestimulator is used to confirm the nerve supply to the rectus abdominismuscle was still intact. Pressure was then applied to the sites whichwere bleeding until hemostasis was achieved.

Hemostasis is then achieved using electrocautery in the bed where therectus abdominis is previously lain. Two JP drains are placed in thepelvis and one is placed in the space where the rectus abdominis istaken form along the left side. These are placed to bulb suction.

The midline wound is then closed using one PDS in running andinterrupted sutures. Skin is then closed using staples. The patient istaken to the Recovery Room. Sponge and needle counts are performed twotimes to ensure accuracy.

                  TABLE 1                                                         ______________________________________                                        Animal Behavioral Data.                                                       Group/              Control +        SCI +                                    Measure    Control  Myoplasty                                                                              SCI     Myoplasty                                ______________________________________                                        Weight.sup.A                                                                             391 ± 35                                                                            375 ± 50                                                                            400 ± 24                                                                           389 ± 40                              Final Tarlov Score.sup.B                                                                 12       12       5*      4*                                       Final Angleboard                                                                         80 ± 5                                                                              80 ± 5                                                                               65 ± 8**                                                                           60 ± 6**                             Score.sup.c                                                                   ______________________________________                                         SCI: Spinal cord injury.                                                      .sup.A : Weight in grams (mean ± S.E.M.) at time of surgery.               .sup.B : Tarlov score (median) prior to sacrifice (4 weeks).                  .sup.C : Angleboard score in degrees (mean ± S.E.M.) prior to sacrific     (4 weeks).                                                                    *p < 0.05 vs. control and control + myoplasty, MannWhitney Utest.             **p < 0.05 vs control and control + myoplasty, MannWhitney Utest.        

                  TABLE 2                                                         ______________________________________                                        Micturtion Pattern.                                                                             Control +         SCI +                                                Control                                                                              Myoplasty                                                                              SCI      Myoplasty                                 ______________________________________                                        Oral intake/24 hr (ml)                                                                     38 ± 5                                                                              41 ± 7                                                                              45 ± 11                                                                           41 ± 5                               Voided volume/24 hr                                                                        16 ± 4                                                                              18 ± 5                                                                              19 ± 4                                                                            17 ± 5                               (ml)                                                                          Number of micturitions                                                                     18 ± 4                                                                              21 ± 5                                                                              9 ± 3*                                                                            10 ± 4*                              Volume per mict (ml)                                                                       0.8 ± 0.2                                                                           0.7 ± 0.1                                                                           2.1 ± 0.5*                                                                        1.9 ± 0.6*                           Ration of night/day mict.                                                                  1.8 ± 0.6                                                                           1.9 ± 0.5                                                                           2.0 ± 0.7                                                                         1.7 ± 0.4                            Largest mict. volume                                                                       1.5 ± 0.4                                                                           1.9 ± 0.5                                                                           3.1 ± 0.7*                                                                        2.6 ± 0.6*                           (ml)                                                                          Smallest mict. volume                                                                      0.1 ± 0.1                                                                           0.2 ± 0.1                                                                           0.8 ± 0.3*                                                                        0.6 ± 0.2*                           (ml)                                                                          ______________________________________                                         SCI: Spinal cord injury.                                                      Mict: Micturition.                                                            *p < 0.05 vs. control and control + myoplasty, ANOVA and Tukey's HSD test                                                                              

I claim:
 1. A method of inducing micturition by a patient comprising thesteps of:a) transecting an abdominal muscle of said patient to create amuscle flap attached, wherein blood supply and innervation to saidmuscle flap is preserved, b) wrapping said muscle flap around saidpatient's bladder and suturing said muscle flap to itself creating amuscle bag around said bladder; c) attaching to said muscle bag or atleast one preserved nerve at least one electrical lead; d) attaching theother end of an electrical lead that is attached to said muscle bag orintercostal nerve to an actuatable signal generator that comprises oneor more switches and a power source; and e) actuating said switch orswitches and delivering a series of stimulus pulses from said signalgenerator to said muscle bag sufficient to cause said muscle bag tocontract.
 2. The method of claim 1 wherein said power source of saidactuatable signal generator is a battery.
 3. The method of claim 1wherein two leads are attached to said actuatable signal generator andto two nerves that innervate said muscle flap.
 4. The method of claim 1wherein a lead is attached to said muscle bag.
 5. The method of claim 1wherein two leads are attached to said actuatable signal generator andto said muscle bag.
 6. The method of claim 1 wherein said stimuluspulses are delivered at a frequency of 1 to 50 Hz, with each said pulsehaving a 0.01 to 1.0 msec pulse duration, 1 to 300 volt amplitude and astimulation duration of up to 3 minutes.
 7. The method of claim 1wherein said stimulus pulses are delivered at a frequency of 10 to 35Hz, with each said pulse having a pulse duration of 0.05 to 0.5 msec andsaid series has a duration of 0.2 to 1 minute.
 8. The method of claim 1wherein said stimulus pulses are delivered at a frequency of 10 to 30Hz, with each said pulse having a pulse duration of 0.3 to 0.5 msec andsaid series has a duration of 0.2 to 1 minute.
 9. The method of claim 1wherein said stimulus pulses range from 1 to 50 volts.
 10. The method ofclaim 1 wherein said actuatable signal generator comprises a switch thatis a radiofrequency controlled electromagnetic switch or a magneticswitch.
 11. The method of claim 1 wherein said actuatable signalgenerator comprises two switches wherein at least one is aradiofrequency controlled electromagnetic switches or magnetic switches.12. The method of claim 1 wherein said actuatable signal generatorcomprises a switch that is a radiofrequency controlled electromagneticswitch.
 13. The method of claim 1 wherein said actuatable signalgenerator comprises two switches that are both radiofrequency controlledelectromagnetic switches.
 14. The method of claim 1 wherein saidactuatable signal generator comprises one switch that is a magneticswitch.
 15. The method of claim 1 wherein at least one lead comprises aspiral nerve electrode.
 16. The method of claim 1 wherein at least onelead is a wire extramuscular lead.